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Mud, mud, glorious abyssal mud

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1 June 2017 - 2:36pm

The beam trawl returns to the deck of the CSIRO RV Investigator with an impressive haul of mud from the abyss. Image: Robert ZugaroMelanie Mackenzie of Museums Victoria with a mud-bathed sea cucumber. Image: Asher Flatt

Day 18: Melanie Mackenzie, Museums Victoria

There is always a buzz of anticipation in the sheltered science workshop as we wait for the crew to call us out to the deck. What will this catch bring up from the abyss? Golden corals? Sea cucumbers with shark-like fins? A strange faceless fish?

This time the trawl seemed to be coming up slowly and we realised why as the winch finally revealed the net – a huge mass of messy mud and tangled limbs and fins. We had prepared tubs with ice, seawater, trays and forceps to retrieve any animals, but this catch would need a new approach.

Finding a way in and turning the first sod. Image: Robert Zugaro.Tina Molodstova of PP Shirov Institute of Oceanography, Russia, and Lupita Bribiesca-Contreras of Melbourne University and Museums Victoria hose the catch with sea water as others wield shovels, sieves and trays to save the day. Image: Asher Flatt

After some quick consultation we sprang into action. Shovels, buckets, plastic containers, sieves, a foldable conveyor table, and most importantly Tina Molodstova and Lupita Bribiesca-Contreras with the seawater hoses.

Sushi train? Image: Robert Zugaro

Little by little we emptied the net, filling tubs full of mud for people to sort and sieve through, and washing mud from the animals in the net – revealing spectacular colours and shapes.

As luck would have it the trawl had come up just before shift change, so everyone pitched in to get specimens to the lab for processing as quickly as possible. The positive of getting so much mud? Animals were preserved in a cool ‘mud cocoon’ and many came up in very good condition.

Thankfully conditions were also perfect for deck work – calm seas and the sun was shining, so after so much time spent inside, scientists revelled in the opportunity to get some fresh air, despite the need for a hose-down and perhaps an extra shower or two afterwards.

Here’s hoping that abyssal mud is good for the skin.

Lauren Hughes of the Australian Museum cradles a mud-cocooned crab: Image: Asher FlattMaggie Georgieva of the Natural History Museum, London, UK, sifts through a tub of mud keeping a keen eye out for her favourite polychaetes. Image: Asher Flatt

Melanie being hosed down by Marc. Image: Asher FlattPhoebe Lewis of Victoria's Royal Melbourne Institute of Technology gets slushy. Image: Asher FlattAnd a fish that emerged from the mud . . . the Elongate Fangjaw (Sigmops elongatus). This fangjaw inhabits the twilight zone in the ocean, so it was probably caught in the net on the way back up. They are protandrous hermaphrodites, changing sex from male to female during their lifecycle. They undertake daily vertical migrations in the water column to feed at night, and the photophores along the underside provide camouflage or countershading, allowing the fish to hide it's silhouette from predators and prey.